Timing device for high-speed motionpicture cameras



Jan. 11, 1949. R. G. STONER ETAL 2,453,332

I TIMING DEVICE FOR HIGH SPEED MOTION-PICTURE CAIERAS Filed on. 4. 1945 Richard Gfiimne? Curtis W. Lam sun Patented Jan. 11, 1949.

TIMING DEVICE FOR HIGH-SPEED MOTION- PICTURE CAMERAS Richard G. Stoner and Curtis W. Lampson, Princeton, N. J.. asslgnors to the United States of America as represented by the Secretary of War Application October 4, 1945, Serial No. 620.3%

1 Claim. (Cl. 346-107) In investigating physical phenomena with the aid of high speed motion picture cameras, it is often desirable to be able to ascertain to a high degree accuracy, the elapsed time between two or-more'events depicted upon the film.

It isa purpose of this invention to provide an attachment for a high speed motion picture camera-whereby a time record is produced upon the film enabling very small time intervals between any two events depicted thereon to be determined.

It is a further object to provide an attachment, as aforesaid, that requires only minor changes in the camera itself and that in no way interferes with the use of the camera without the attachment, when desired. 8

Another object is to provide an attachment wherein thetime record appears upon a portion or the film ordinarily not used for recording events.

,A still further object is to provide a time recording attachment ior motion picture cameras of the type wherein the film is continuously moved, wherein the time interval measured may be-widely varied so that the most favorable interval for the events to be depicted may be selected.

Another object is to provide a time-recording attachment for motion picture cameras that is relatively inexpensive, easy to construct and attach, and extremely reliable in operation.

Other objects and advantages of the invention will become apparent as the description proceds.

In the drawings:

Fig. 1 shows a portion oi a motion picture camera with side cover removed to illustrate the general arrangement of lens, film, sprocket, and timing projector,

Fig. 2 is a view on line 2-2 of Fig. 1, of a portion of the sprocket and projector showing the positioning of the projector transversely of the film,

Fig. 3 is an enlarged section taken upon the line 3-4, Fig. 2 and showing the projector casing, lamp, lens and contact terminals,

Fig. 4 is a diagram of the tube and circuit used to periodically fiash the projector lamp at predetermined time intervals,

Fig. 5 is a view of a section of exposed film showing the time trace thereon, and

Fig. 6 is a view, partly in section, showing the manner in which a lens satisfactory for use in the projector, may be obtained.

At 0 is indicated a portion of the casing of a high-speed motion picture camera having a back wall, a cover, hinged at H, and a prism lens L adapted to be rotated, by mechanism not shown, in timed relation with movement of a film F passing continuously over and about a support or sprocket wheel S. The numeral l indicates the casing of a neon lamp, fixed in any suitable manner to the wall of the camera (as, by a bracket i' having a foot flange secured to the back wall of the camera, as shown) and having a lens 2 positioned closely adjacent the film so as to project light onto the space between one edge of the film and the adjacent row of sprocket openings therein, all as is clearly indicated in Fig. 2, where it may be seen that the lens is a converging lens projecting a pencil of rays to a'point at the film. Insulated terminals 3 and t are secured through one side of the camera wall whereby to provide external connections for leads 5 and 6 for the lamp-flashing circuit.

Referring to Fig. 3, the lamp casing may consist of a section of metallic tubing I, closed at one end by a plug l and at its other end by an insulating plug 8. A small hole or light port 9 such as that made by a #55 drill, is bored through the lamp casing wall at a point approximately mid-way between the ends of the casing, and a lens holder Ill is secured to the casing concentric with hole 9. This holder may consist of a short section of metallic tubing of the same diameter as casing i and shaped at one end to fit the casing. The holder is secured to the casing I in any convenient manner, as by soldering. The outer end of the holder i0 is counterbored as at H to receive the lens 2 which may be secured in place by spinning the reduced wall of the holder about the adjacent portion of the lens.

The insulating plug 8 has a reduced portion fitting within the end of easing l and secured therein by threading, rivets or any other suitable means. the internal connector wires from the electrodes of a small neon or argon lamp l2 having a fairly snug fit within casing I. Terminals l3 and It are secured to the outer end of the plug 8, and

the connector wires are attached thereto, whereby soldering connections may be made with intermediate external lamp leads 5 and 6 extended to the terminals 3 and E as in Fig 1. A lamp l2 of 1/25 watt size was found satisfactory in one installation built and successfully operated.

The flashing circuit for lamp i2 is shown at Fig. 4. A triode ii of the heater cathode type, such as the 6J5, is connected in a modulating The plug 8 receives therethrough auaeaa circuit having an input it to apply an alternating voltage of the desired. frequency to the gird and has a parallel connected resistor II. A second resistor It is connected in series to the plate through the "B" circuit II. A lead 20 extends from a connection between resistor II and the plate, to terminal 3 on the camera, while a second lead 2|, extends from the cathode to terminal '4. When the grid potential rises to the point where the tube conducts, the flow oi plate current creates a voltage drop across resistor II to thus extinguish the lamp l2. During the part of the cycle that the grid is below cut-oil, the plate voltage rises and the lamp is lighted to thereby expose the film and form thereon a short dash having sharply-defined ends. Fig. 5 shows a film F wherein the exposed dashes are indicated at 22 in conjunction with the image 23 oi a rapidly moving object such as an indicator.

By applying an alternating voltage to input i6 having a known frequency, the time interval between dashes'upon the film is known exactly and may be used to measure the intervals between events depicted upon the film with a high degree of accuracy. For example, where a 1000- cycle control signal is used, time intervals to 0.1 milliseconds may be estimated. Furthermore, the timebetween exposures may be computed, as well as the speed of the film. Fig. 6 shows one manner of obtaining a suitable lens. The bulb of a flashlight of the fountain pen type is cut oil? along the plane indicated at 24. The lens thus obtained will have a focal length of about 6 mm. and when used to give unit magnification, allows an overall distance of source to image of about 30 mm.

The operation will be obvious from the foregoing description. Actual tests of the model selected for description indicate that successful operation is possible at film speeds up to at least 8300 feet per second.

While we have disclosed a specific embodiment of our invention as it is now known to us, various 4 modifications, rearrangement of parts, and substitutions o! equivalents, will occur or be obvious to those skilled in the 'art. Hence the foregoing description is to be taken in an illustrativeand not a limiting sense; and we wish to reserve all such modifications and substitutions as fall within the scope of the sub-joined claim.

Having now fully disclosed our invention, what we claim as new and desire to secure by Letters Patent is:

In a high speed photo film strip moving picture camera, a timing device to produce a time calibration record on the film strip while passing through the camera comprising an opaque closed hollow cylinder having a mounting bracket attachable to the wall of a camera adjacent the film path, said cylinder having a light port therein on a radius of the cylinder distant from said bracket, a gaseous electric discharge light source in said cylinder responsive to high frequency intermittent electrical discharges to propagate correspondlngly intermittent light rays through said port, said cylinder having a lateral tubular ex tension concentric with the said radius of the cylinder, and a converging lens mounted in said tubular extension.

RICHARD G. STONER. CURTIS W. LAMPSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,599,538 Mintrop Sept. 14, 1946 2,045,414 Rumpei June 23, 1936 2,077,390 Blaw Apr. 20, 1937 FORHGN PATENTS Number Country Date 569,475 France Apr. 12, 1924 604,860 France Mar. 15, 1926 

